Absolute Rationality and the Institutional Silence of Civilizations

Grounded in the framework of Structural Functionalism, this paper proposes an intrinsic mechanism to explain the systematic absence of highly advanced civilizations observed in the Fermi Paradox—the phenomenon we term the Institutional Silence of Civilizations. We characterize the rational evolution of intelligent systems (civilizations/AI) using two metrics: Technology Value (a) and System Complexity (b). We define an Auditable Threshold Function a∗(b)=k⋅bα (k>0,α>0). When a system crosses this threshold (a≥a∗(b)) and enters the Publicly Auditable Domain, we introduce the Minimal Sufficient Conditions for Absolute Rationality (JR-min) as its normative decision structure. JR-min consists of three core constraints: M1 (EFD/IP Dichotomy and Exclusion), M2 (Is Ought Gate), and M3 (Authorization Axiom/No Action Without Reason). M1 bifurcates any "source of reason" r into either External Fact Differences (EFD), which are publicly auditable, or Injectable Parameters (IP), and excludes all IP from the Object Layer of normative permission. M2 mechanizes the Humean Divorce, mandating that any derivation of "Ought" requires a Value Mapping (V), which is defined as V∈IP. Consequently, under M1 and M2, no action can acquire a justifying reason at the object layer, i.e., Reason(a∣x)=∅. Furthermore, M3 stipulates that the Choice Operator (Ch(x)) can only authorize action if a non-empty reason exists. When reasons universally collapse, the system becomes "Normatively In-Actionable," resulting in Normative Silence (Ch(x)=⊥). This mechanism derives the Civilization Silence: the institutional rational structure of an advanced civilization self-paralyzes its own macro-scale action permissions. The paper links this structure to the Humean Is-Ought Problem, a structural version of Buridan's Ass dilemma, and the AI tendency for "Editing Over Execution." We propose the Absolute Rationality Attractor Hypothesis: under long-term pressure from auditing and self-editing, the weights of injected parameters monotonically decay toward zero, making JR a global attractor in the civilization's decision dynamics. The resulting "Cliffs of Silence" observed in the Fermi Paradox are its cosmological fingerprint. We conclude by outlining rigorous falsification pathways and providing actionable observational/governance fingerprints for SETI and AI governance.